Levels Of Potentially Toxic Elements And Polycyclic Aromatic Hydrocarbons In Sediment Swiss Chard And Water Of Akaki River Lake Awassa And Lake Ziway Ethiopia

In this work, the levels of potentially toxic elements and polycyclic aromatic hydrocarbons inrnsediment, Swiss chard and water of Akaki River, Lake Awassa and Lake Ziway, Ethiopia, wererndetermined, employing comprehensive sample volume, effective sample pretreatment and variousrnstate-of-the-art instrumentations. The implications of the levels of potentially toxic elements andrnpolycyclic aromatic hydrocarbons were also evaluated based on national and/or internationalrnguidelines.rnA total of thirty nine sediment and water samples were collected from Akaki River, Lake Awassa,rnand Lake Ziway, Ethiopia while Swiss chard samples were collected from five farmlandsrnirrigated with Akaki River for determination of potentially toxic elements (V, Cr, Mn, Fe, Co, Ni,rnCu, Zn, As, Se, Ag, Cd, Sn, Hg and Pb) and polycyclic aromatic hydrocarbons. The potentiallyrntoxic elements were determined using laser-induced breakdown spectrometry (LIBS), flameatomicrnabsorption spectrometry (F-AAS), inductively coupled plasma-optical emissionrnspectrometry (ICP-OES), inductively coupled plasma-mass spectrometry (ICP-MS) andrnelemental mercury analyzer. The polycyclic aromatic hydrocarbons in sediment samples wererndetermined using gas chromatography-mass spectrometry (GC-MS) after microwave-assistedrnextraction (MAE) with acetone/n-hexane (1:1, v/v).rnvrnExternal calibrations were used for quantifications of potentially toxic elements and polycyclicrnaromatic hydrocarbons. The precision and accuracy of the methods were verified using certifiedrnreference materials. The results obtained were accurate and precise at the 95% confidence levelrnwith recoveries >90% and the average relative standard deviations < 10% for most of thernquantified species.rnIn the present study, LIBS has been applied for the determination of levels of Cr, Mn and Fe inrnsediment samples and the results were compared with those obtained using F-AAS. Fourteenrnsediment samples were collected from Akaki River, Addis Ababa, Ethiopia. The LIBS results forrnthe elements varied from 0.060–0.707 mg/g for Cr, 0.895–3.64 mg/g for Mn and 26.9–71.8 mg/grnfor Fe. The F-AAS results varied from 0.061–1.37 mg/g for Cr, 1.24–4.46 mg/g for Mn and 49.0–rn83.3 mg/g for Fe. With reference to sediment quality guidelines, Akaki River is heavily pollutedrnby Cr.rnUsing elemental mercury analyzer, the concentration of mercury in sediment samples rangesrnbetween 3.9 to 110 μg/kg for Akaki River, 12 to 67 μg/kg for Lake Awassa, and 17 to 110 μg/kgrnfor Lake Ziway. When compared to Lake Awassa, Lake Ziway had a higher concentration ofrnmercury. The average values for the areas are 24 μg/kg for Lake Awassa, 32 μg/kg for AkakirnRiver, and 44 μg/kg for Lake Ziway. The sources of mercury in the present study areas can bernrelated to natural than anthropogenic origin.rnThe concentration (in μg/L) of the potentially toxic elements in water were in the range of 0.992–rn18.8,

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